1. Field of the Invention
This invention relates to a durable composition for tire carcass which is composed of polymer blend suitable for preventing separation at the ends of turn-ups of carcass reinforcing cords in tires for automobiles.
2. Prior Art
The conventional rubber polymers used for carcass cords are generally natural rubber (ab. NR) or blend of natural rubber and butadiene rubber (ab. BR). But the degree of the penetration of said polymers into carcass ply cords is low. The addition of a lot of softeners or adhesives for covering said defect results in the deterioration of properties of said polymers. Thus there have not been obtained the integral structure of carcass ply cords and rubber polymers. Consequently, under high-frequency vibration inevitable to automobile tires, cracks in rubber polymers are induced by the concentration of stress at the interfaces between the filaments of carcass ply cords and said rubber polymers, by flex fatigue of the rubber polymers or by the deterioration of adhesive properties. And the growth of said cracks causes the separation failure. Thus, it can be said that considerations have not been taken into consideration when adapting rubber polymers to carcass ply cords.